Ignition distributor

ABSTRACT

The advance curve of an ignition distributor is tailored to provide a desired degree of advance at cranking speed, a desired degree of retardation at low or engine idling speed, and thereafter a normal advance curve as the engine speed increases. The desired curve is obtained by the use of two sets of centrifugal weights carried by an intermediate plate and having pins engaging in respective cam slots of a lower plate fixed to the distributor shaft and an upper plate fixed to the distributor cam.

United States Patent 72} Inventor [56] References Cited UNITED STATES PATENTS Roger Habert Paris, France M 6? 6 6 4WWM4 006 y W 4 2 2 1 1 3 2 l WW6 m mm n" maomau ttfl nun 33mm 8 hmwmwo l i mmGHBs 556679 666666 999999 111111 26852 11 1 550909 925275 0 8702 225628 2 2 2 2 3 4 333333 .R

France Primary Examiner-J. R. Scott Attorney-imirie & Smiley P.B.l 61489 ignition distributor is ABSTRACT: The advance curve of an tailored to provide a desired de [54] IGNITION DISTRIBUTOR speed, a desired degree of retardation at low or e speed, and thereafter a normal advance curve 200/1911, speed increases. The desired curve is obtained by the use of 200/32, 200/80 two sets of centrifugal weights carried by an intermediate plate and having pins engaging in respective cam slots of a ...H0lh 19/00 [51] Int.

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200/ 19- lower plate fixed to the distributor shaft and an upper plate 32, 80; 123/1 17, 146.5; 64/25 fixed to the distributor cam.

Patented May 18, 1971 M! VLN TOR Poem fiwmr IGNITION DISTRIBUTOR BACKGROUND OF THE INVENTION The emission of unburned hydrocarbons and carbon monoxide in the exhaust gases of internal combustion engines constitutes a source of air pollution which recently has become the subject of much concern. In copending application Ser. No. 702,958, now U.S. Pat. No. 3,482,559, filed Jan. 5, 1968, an ignition distributor is disclosed which employs a set of centrifugal weights mounted upon an intermediate plate cranking speed, the desired ignition advance for'effec'tin'geasy starting of the engine is achieved, whereafter at engine idling and/or low engine speed the distributor is retarded and thereafter a normal distributor advance curve is achieved as the distributor shaft rotational speed increases.

The retarding action of the device at low engine speed eliminates much of the problem of emission due to the rich mixture required for idling and low speed engine operation by retarding the ignition spark timing to such a degree that the hydrocarbons and carbon monoxide are burned more completely thus reducing the emission characteristics of the engine at low engine speeds.

Wit the arrangement as above-described, it has been found that the action of the cam slots on the pins may cause a' certain amount of binding which disturbs the desired retard-advance characteristics of the distributor and which may display a hysteresis type of action resulting in different advance-retard characteristics as the distributor shaft is accelerated and decelerated.

BRIEF SUMMARY OF THE INVENTION It is, therefore, of primary concern in connection with the present invention to provide an improved distributor assembly wherein the desired advance-retard characteristics are more faithfully achieved. Basically, the present invention achieves this end by utilizing a pair of centrifugal weights for achieving the requisite advance characteristics and a pair of auxiliary centrifugal weights for achieving the desired retard characteristics. The auxiliary weights operate only over a small range of engine speed and thereafter are ineffective to produce any further action so that over a large range of engine speed, only the main weights and their associated pins and cam slots are in operation so as to minimize the possibility of binding which might otherwise occur.

BRIEF DESCRIPTION OF THE DRAWING FIGURES FIG. I is a vertical section taken through a distributor constructed according to the present invention;

FIG. 2 is a top plan view of the assembly shown in F IG. 1;

FIG. 3 is a horizontal section taken through the assembly shown in FIG. I and illustrating the auxiliary weights; and FIG. 4 is a graph illustrating the retard-advance characteristics achieved by a distributor according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION As is shown in FIG. I, the distributor includes the rotor shaft 1 which, as is conventional, is directly driven by the associated internal combustion engine, frequently by gear connection to the cam shaft. Fixed to the distributor I is a lower plate member 2 which is thereby caused to rotate in unison with the shaft, and two other plates are associated with the shaft, the upper plate 16 and the intermediate plate 6-. The intermediate plate 6 is fixed to the bushing 7 joumalcd on the distributor shaft 1 below the distributor cam 17 which, in tum is rotatably mounted on the shaft 1, and the plate 16 is fixed to the distributor cam so as to rotate in unison therewith.

As may be seen in FIGS. 1 and 2, the intermediate plate 6 is provided with a pair of diametrically opposed pins 8 and 9 which mount two sets of centrifugal weights for pivotal motion thereabout. The main weights are indicated by the reference characters 14 and 15 and are disposed uppermost as is shown in FIG. 1, and the auxiliary weights are indicated by the reference characters 10 and 11, see also FIG. 3. It will be appreciated that the intermediate plate 6 is free floating with respect to the the distributor shaft 1 but that it is normally urged to a predetermined and preselected rotational position with respect thereto under the action of the tension spring 22 which is anchored at one end on an upturned tab 24 rigid with the plate 6 and at its opposite end with a pin 23 fixed to the lower plate 2 and upstanding therefrom to project through the enlarged opening 60 in the intermediate plate 6, see particularly FIG. 3. Likewise, the upper plate 16 and the distributor cam 17 are free floating normally with respect to both the intermediate plate and the distributor shaft but it will be appreciated that the upper plate is normally urged to a preselected rotational position with respect to the intermediate plate 6 under the action of the tension spring 25 anchored at one end to the upstanding tab 27 on the intermediate plate 6 and its opposite end on the depending pin 26 fixed to the upper plate 16.

The auxiliary weights l0 and I1 carry respective depending pins 12 and I3 which project through enlarged openings 6a and 6b in the intermediate plate 6 and engage within respective cam slots 3 and 4 formed in the lower plate 2, the pitch or inclination of the cam slots 3 and 4 being such as to impart counterclockwise rotation of the intermediate plate 6 with respect to the distributor shaft when the weights 1'0 and 11 fly outwardly in the directions of the arrows F as viewed in FIG. 3. Since the upper plate 16 is coupled to the distributor shaft 1 through the intermediary of the intermediate plate 6, corresponding motion will be imparted to the upper plate 16. However, at the same time, the upper weights 14 and 15 move outwardly in the direction of the arrows F in FIG. 2 and the upstanding pins 18 and 19 carried by these respective weights operating in the cam slots 20 and 21 respectively of the upper plate 16 impart clockwise rotation of the upper plate 16 with respect to the intermediate plate 6.

A tension spring 28 may be provided between a tab 29 upstanding from the upper plate 16 and connected to a pin 18 so as to impart greater resistance of the weights 10 and 11 to centrifugal force so that the operation of the weights 14 and 15 lags that of the weights I0 and 11 as the rotational speed of the distributor 1 increases. The pitches of the cam slots 3 and 4 as compared with the cam slots 20 and 21 are different so that their initial effect is to produce retardation of the ignition timing, it being appreciated that the usual contact breaker plate is provided about the upper plate 16 and upon which the breaker points are mounted. This breaker may of course be vacuum controlled as desired.

By providing a sufficiently strong tension spring 28 to retard the action of the weights l4 and 15 with respect to the weights 10 and 11, an ignition advance curve characteristic as is illustrated in FIG. 4 may be achieved. In FIG. 4, the ordinate represents increasing ignition advance while the abscissa represents rotational speed of the distributor shaft 1 of the associated internal combustion engine. At engine cranking speed, as is illustrated within the ignition advance range A, the advance is tailored to achieve easy starting of the engine and as soon as the engine starts and the speed increases, the action of the weights l0 and II will cause retardation of the ignition spark as indicated by line C in FIG. 4 until the pins 12 and 13 reach the ends of their respective slots 3 and 4 whereafter the ignition timing will remain constant as illustrated by line B in FIG. 4. The engine speed then increases until the effect of the tension spring 28 is overcome and the weights l4 and 15 begin to move outwardly to advance the ignition timing as is illustrated by line D in FIG. 4 and the curvature of the slots 20 and 21 may be tailored to provide a definite and increasedignition advance as illustrated by the line E.

Thus, it will be appreciated that by adjusting the curvatures or pitches of the cam slots 3 and 4 and of the cam slots 20 and 21 and by varying the relative tensions of the various springs urging the weights and 11 and the weights l4 and 15 to their inward positions, various retard-advance characteristics may be achieved as may be desired.

lclaim:

1. An ignition distributor for internal combustion engines comprising, in combination:

a rotatable distributor shaft,

a mounting member rotatably carried by said shaft,

a distributor cam journaled on said shaft,

centrifugal weight means carried by said mounting member reacting between said distributor shaft and said cam for imparting rotation to the latter first in one direction relative to said shaft and then in the opposite direction relative to said shaft in response to increasing rotational speed of said shaft, said centrifugal weight means including first and second centrifugal weights pivotally mounted on said mounting member and reacting with said shaft and said cam, respectively,

a plate fixed to said shaft, and

a plate fixed to said cam, said mounting member being in the form of a plate intermediate the first mentioned plates, said first mentioned plate being provided with cam slots, and said first and second centrifugal weights having pins engaged in respective ones of said cam slots.

2. The ignition distributor as defined in claim 4 wherein said first centrifugal weight reacts with said shaft to impart relative rotation of said mounting member with respect to said shaft in said one direction, and said second centrifugal weight reacts with said cam to impart relative rotation of said cam with respect to said shaft in said opposite direction. 

1. An ignition distributor for internal combustion engines comprising, in combination: a rotatable distributor shaft, a mounting member rotatably carried by said shaft, a distributor cam journaled on said shaft, centrifugal weight means carried by said mounting member reacting between said distributor shaft and said cam for imparting rotation to the latter first in one direction relative to said shaft and then in the opposite direction relative to said shaft in response to increasing rotational speed of said shaft, said centrifugal weight means including first and second centrifugal weights pivotally mounted on said mounting member and reacting with said shaft and said cam, respectively, a plate fixed to said shaft, and a plate fixed to said cam, said mounting member being in the form of a plate intermediate the first mentioned plates, said first mentioned plate being provided with cam slots, and said first and second centrifugal weights having pins engaged in respective ones of said cam slots.
 2. The ignition distributor as defined in claim 4 wherein said first centrifugal weight reacts with said shaft to impart relative rotation of said mounting member with respect to said shaft in said one direction, and said second centrifugal weight reacts with said cam to impart relative rotation of said cam with respect to said shaft in said opposite direction. 